The present application relates to a molecular device, a single-molecular optical switching device, a functional device, a molecular wire, and an electronic apparatus. In particular, the present application relates to a molecular device, a single-molecular optical switching device, and a functional device each of which uses an electron transfer protein such as zinc cytochrome c, a molecular wire which is suitable for being used in a wiring in various devices, and an electronic apparatus using the functional device.
In the world of the electronics devices each using the semiconductor in an information communication field, a computer field, and the like, the miniaturization technology has been developed for the purpose of enhancing the performance of the electronics devices. However, the physical limit of the miniaturization technology, has been almost here, and thus the breakthroughs by a new engineering innovation are desired. An electronic circuit using molecules, and a molecular device technology can be given as one of the breakthroughs. The molecular device functions on the order of angstroms in size, and thus the integration level of the molecular device can be improved 103 to 106 times as high as that of the semiconductor device. This, for example, is described in a non-patent literary document of “Molecular Nano-Technology: Developing of Ability of Molecule into Device Development”, by Kazumi Matsusige and Kazuyuki Tanaka, KAGAKU-DOJIN PUBLISHING CO., LTD.
With regard to the principles of driving the molecular device, and the model thereof, several proposals have been made.
Batlogg et al. obtained a knowledge that the characteristics of the conductivity or the superconductivity develop in a crystal of an organic matter, or the like by using the technology of the field effect transistor (FET). This knowledge is described in a non-patent literary document of J. H. Schon, Ch. Kolc, B. Batlogg: Nature, 406, 702(2000). The characteristics are found out in a fullerene and a metallic complex as well, and thus attract attention now because they can be expected to give each of the various compound molecules a switching function through the carrier doping by an electric field.
In addition, Wada et al. proposed a model of a molecular single-electron transistor including the fullerene in the form of a quantum dot as the possibility of the single-molecular device. This technique is described in Japanese Patent Laid-Open No. Hei 11-266007. This technique is such that an electrode is joined in the form of a tunnel junction to the quantum dot, and a gate voltage is applied to the electrode through an insulating layer to change a potential of the quantum dot, thereby developing a function as a transistor.
Moreover, there is also an attempt to use a supermolucule showing various structural and functional properties, and to apply a molecule recognizing function thereof to switching. The supermolucule is such that a plurality Of molecules are organized by utilizing a noncovalent bond-like interaction such as coordinate bond, hydrogen bond or an intermolecular force, thereby acquiring the various structural and functional properties each of which may be impossible in a state of a single molecule. Balzani et al. proposes a molecular switch which a behavior changes due to an external field such as pH or a light by utilizing a supermolecular compound, such as catenane or rotaxane, having a molecular recognizing function. This technique, for example, is described in a non-patent literary document of V. Balzani, A. Credi, and M. Venturi: Coord. Chem. Rev., 171, 3 (1998).
On the other hand, with regard to a wiring technique in the molecular device, there is an attempt to introduce a functional group such as thiol to a terminal of a conductive polymer molecule to perform wiring connection by utilizing chemical adsorption of the conductive polymer molecule for a gold or ITO electrode.
Although many researches about the molecular device have been made so far, as has already been described, the technique with which the practical molecular device or the circuit using the same can be configured is not yet provided as the case now stands.
In the design or configuration of the molecular device or the circuit using the same, it becomes a problem how the disposition and arrangement of the individual molecules, the recognition of the individual molecules, the access to the individual molecules, the wiring for formation of a circuit by minutely connecting specific molecular devices to one another, the addressing and the like are carried out. For example, although the technology for disposing atoms on a one-by-one basis by using a scanning probe microscope (SPM), or the like has been developed for the disposition and arrangement of the individual molecules described above, such a technique is not realistic in terms of the design or configuration of the device on the order of nanometers in scale. In addition, with regard to the wiring described above, it is thought that when the molecular device described above is designed, it is realistic to drive the molecular device by using an electrical signal in the solid similarly to the case of the semiconductor device. However, it is very difficult to connect a macro-scale conducting wire to the molecular level device.
On the other hand, it is thought that in the design or configuration of the molecular device or the circuit using the same, a molecular wire which is formed in the form of a single chain polymer or one-dimensionally integrated molecules is an important factor in a conductive path or the molecular device having a switching function by itself. For a viewpoint of this, the molecular wire has been studied. However, in the case of the molecular wire which is currently studied, a conduction mechanism thereof is not sufficiently resolved as the case now stands. In addition, there is a problem that it is not easy to form the molecular wire because in general, the conductivity of the simple one-dimensional material is impaired due to the property, such as the Peierls transition, peculiar to the one-dimensional system.
In addition, with regard to a metallic complex chain expected as the molecular wire, especially, a ladder type metallic complex, a theoretical study about the property thereof is started by Rice et al. In the case of the ladder type structure called a spin ladder having an even number of antiferromagnetic metallic chains arranged therein, it is anticipated that the metallic complex having the ladder type structure shows the superconductivity through the carrier doping. Thus, there is also conceivable the possibility that the metallic complex having the ladder type structure functions as a device. This, for example, is described in a non-patent literal) document of T. M. Rice, S. Gopalan and M. Sigrist: Europhys. Lett., 23, 445 (1993). As an experimental example, double-stranded ladder type compounds each having a copper oxide used therein are synthesized, and it is found out that the resulting compound shows a superconductivity phenomenon under a high pressure. This, for example, is described in a non-patent literary document of M. Uehara, T. Nagata, J. Akimitsu, H. Takahasi, H. Mori and K. Kinoshita: J. Phys. Soc. Jpn., 65, 2764 (1996). In addition, the formation of the molecular wire by dispersing a halogen bridge metallic complex covered with an organic paired anion into a solvent is studied by Kimizuka et al. This study results are disclosed in a non-patent literary document of N. Kimizuka, N. Oda, T. Kunitake: Inorg. Chem. 39, 2684 (2000). Moreover, a ladder type compound using a metallic complex ba p-EPYNN and Ni (dmit)2 is also studied. This study results, for example, are disclosed in a non-patent literary document of H. Imai, T. Inaba, T. Otsuka, T. Okuno, and K. Agawa: Phys. Rev. B54, R6838 (1996). Furthermore, a so-called crossbar switch for controlling switching at an intersection point at which nanowires are made to run at right angles with each other in accordance with an input from the nanowire is thought to be a candidate of the nanodevice not requiring any of the complicated processes. In recent years, the crossbar switch has been actively studied. This study results, for example, are disclosed in a non-patent literacy document of James R. Heath, Philip J. Kuekes, Gregory S. Snider, R. Stanley Williams: Science Vol. 280 (1998). If an array using the nanowire described above can be structured at the molecular level and from bottom up, it is expected from a viewpoint that a very dense device can be realized with relative ease.
However, both the molecular wire and the nanowire described above merely result from the anticipation or the opinions in the experimental stage, and thus lack the practical utility and the specifics. It is difficult to attain those by utilizing the existing techniques, and thus it is desirable to provide a new technique with which the molecular level wiring or the like can be realized at the molecular level and from the bottom up. On the other hand, a synthesis example of a metallic complex integrated structure is also reported in a non-patent literary document of W. Huang, S. Gou, D. Hu, S. Chantrapromma, H. Fun, and Q. Meng: Inorg. Chem., 40, 1712 (2001). In many cases, however, the molecules are merely arranged in a ladder shape in terms of results by a weak interaction such as an intermolecular force. Thus, there is a problem that it is difficult to perform packing control. In addition, the arrangement of the resulting molecules in the metallic complex chain greatly depends on the molecular form, the effect of the substituent group, the delicate interaction between the molecules, and the like. As a result, there is a problem that the molecular wire or the like may not sufficiently function as a single wire because even if the chemical modification is performed for the molecular wire or the like, the probability that the molecular wire or the like can take the ladder type structure or the like is low.
Note that, it is reported that in a specimen in which zinc (Zn) cytochrome c is adsorbed at random onto a nano-porous titanium oxide (TiO2) electrode, the electrons excited by radiation of a light to zinc cytochrome c are injected to a conduction band of the nano-porous titanium oxide, thereby generating a photocurrent. This report, for example, is described in a non-patent literary document of Emmanuel Topoglidis, Colin J. Campbell, Emilio Palomares, and James R. Durrant: Chem. Commun. 2002, 1518 to 1519.
In addition thereto, it is reported that in a single molecular film having a two-layer structure of iron (Fe) cytochrome c immobilized onto a gold substrate, and a green fluorescent protein (GFP), the radiation of a light thereto results in generation of a photocurrent. This report, for example, is described in a non-patent literary document of Jeong-Woo Choi and Masamichi Fujihira: Appl. Phys. Lett. 84, 2187 to 2189 (2004).
It is noted that in a single molecular film which is made of peptide and which is immobilized onto a gold substrate, the radiation of a light thereto results in generation of a photocurrent. This report, for example, is described in a non-patent literary document of Shiro Yasutomi, Tomoyuki Morita. Yukio Imanishi, Shunsaku Kimura: Science 304, 1944 to 1947 (2004). In the technique described in the non-patent literary document of Shiro Yasutomi, Tomoyuki Morita, Yukio Imanishi, Shunsaku Kimura: Science 304, 1944 to 1947 (2004), two kinds of peptides having optical responsibilities different from each other are immobilized onto one gold substrate through a simple molecular film made of disulfide as a sulfur compound which results in that a polarity of the photocurrent is controlled in accordance with a wavelength of the radiated light.
In addition, a method of synthesizing zinc cytochrome c is reported in a non-patent literary document of Martin Braun, Stefan Atalick, Dirk M. Guldi, Harald Lanig, Micael Brettreich, Stephan Burghardt, Maria Hatzimarinaki, Elena Ravanelli, Maurizio Prato, Rudi van Eldic, and Andreas Hirsch: Chem. Eur. J. 9, 3867 to 3875 (2003).
Also, a method of forming a gold electrode onto which a single molecule of iron cytochrome c is adsorbed is reported in a non-patent literary document of Ryutaro Tanimura, Michael G. Hill, Emanuel Margoliash, Katsumi Niki, Hiroyuki Ohno, and Harry Gray: Electrochem. Solid-State Lett. 5, E67-E70 (2002).